Apparatus for controlling the registration curve of electric meters



Sept. 10, 1929. F KURZ Er AL 1,727,509

APPARATUS FOR OONTROLLING THE REGISTRATION CURVE OF ELECTRIC METERS Filed Dec. 21, 1925 |08 LOAD IN PERCENT OF FULL LOAD ormzy Patented Sept. 10, 1929.

UNITED STATES PATENT OFFICE.

FRED KURZ AND ROSCOE WILMETH, OF SPRINGFIELD, ILLINOIS, ASSIGNORS T SAN- GAMO ELECTRICCOMPANY, OF SPRINGFIELD, ILLINOIS, A CORPORATION 0F ILLI- N OIS.

APPARATUS FOR CONTROLLING THE REGISTRATION CURVE 0F ELECTRIC `METERS.

Application led December 21 1925. Serial No. 76,718.

Our invention relates to integrating electricmeters and analogous instruments, and is peculiarly appropriate to meters comprising an armature, usually in the form of a thin metallic disc of suitable conducting material, such as aluminum, arranged to rotate in an air gap between the polesfof two electro-magnets, energized respectively by potential and series coils, said disc being caused to rotate under the influence of two magnetic circuits, a portion of the magnetism from each of which passes through the disc. It is customary to so arrange the magnetic circuits that certain of the paths are common to both circuits. In suchmeters, the structural and operating characteristics of which will be more particularly explained later, in accordance with the usual theory7 the driving torqlue will be proportional to the product of tie two magnetic iields threading the disc into the sine of the time angular phase displacement existing between them. If the angle and the flux from the potential coil remain constant, then the driving force will increase directly with the current in the series coils, and such is usually the case within the working range of ordinary watthour meters. lVhat is more desirable is to have the disc rotate at a speed which varies directlyY with the driving force, but such condition is seldom realized for reasons that will be hereinafter explained. One of the objects of our invention is to provide an improved method` and means for practicing such method. by which the speed of rotation of the disc may be caused to vary directly with the driving force. or be maintained in true proportion to the load within the entire working range of the instrument. Another of our objects is, generally, to provide for controlling as desired tlie shape of the registration curve, and, more particularly, the load registration curve, of such meters. lVe accomplish these objects as illustrated in the drawings and as hereinafter described. TVhat we regard as new is set forth in the claims.

In the accompanying drawings, in which we have illustrated our invention as applied to an induction watthour meter of a well known type, in such manner as to control the load registration curve thereof,-

Fig. 1 is a diagrammatic perspective view illustrating the principal parts of` such a meter;

Fig. 2 is a diagrammatic front elevation illustrating the usual two C-.shaped laminated electro-magnets used in such meters, the potential and series coils associated respectively therewith, and their connections;

Figs. 3, 4 and 5 are diagrammatic views illustrating various Ways in which our invention may be applied; and

Fig. 6 is a chart showing several load registration curves. A

Referring to the drawings, in which Figs. 1 and 2 show the general construction of an induction watthour meter of the type shown and described in Letters Patent to Robert C. Lanphier, N o. 1,010,272, dated November 28, 1911, it will be seen that the meter comprises two electro-magnets 7, 8 in the form of C- shaped steel laminations, the laminat-ions 8 being arranged at right angles to the lower pole 9 of the magnet 7, and being secured in ixed relation thereto so that an air gap 10 is provided between the pole pieces or projections 11, 12 of the magnet 8 and the upper pole piece or projection 13 of the magnet 7. As shown in Fig. 2, the poles 11, 12 are provided With inward extensions 14, 15, respectively, separated by an air gap 16, and the pole 13 overlies such extensions and the air gap 16. The meter also comprises an armature in the form of a thin conducting disc 17 5 preferably of aluminum, which is delicately pivoted so that it may rotate freely about a central axis 18, and so arranged that its outer periphery lies in the air gap 10 and moves therethrough as the disc rotates. The oppo, site peripheral portion of said 'disc is arranged to rotate between the jaws of permanent damping magnets 19, 20. A U-shaped return plate 21, composed of U-shaped steel laminations, is associated with the pole 13 of the magnet 7 so as to embrace the lower end thereof and to occupy a position opposite and adjacent to the poles 11, 12 of the maget 8.

Mounted upon the upper portion of the magnet 7 adjacent to the pole 13 thereof is a 'potential lmagnet 7.

coil 22 composed of a large number of turns of insulated wire which, as shown in Fig. 2, is connected across the line wires 23, 24 over which the customer receives the electrical energ t required for operating the various devices connected to the circuit, and mounted upon the two opposite arms of the magnet 8 are coils 25, 26 composed of a few turns of insulated wire which, as shown in said ligure, are connected in. series with the translating devices 27 -which the customer may connect to the supply lines 23, 24. Asis well known to those familiar with the art, the establishment of any current in the series windings 25, 26 serves to create a magnetic field in the air gap 10 which has as its magnetic circuitthe C-shaped laminations ofthe series magnet 8, the air gap 10, and the pole 13 of the The return plate 21 serves as an additional path for the magnetism originating in the series magnet 8. The moment the load 27 is applied to the lines 23, 24, current is established in the coils 25, 26, with the result that' a shifting magnetic field perpendicular to the plane of the dise 17 is created within the air'igap 10, and there is simultaneouslv created a force which tends to'rotate the isc 17 in a direction dependent upon the relative manner in which the coils (25, 26 and the coil 22 are connected into the system. In accordance with the usual theory, the driving torque will be proportional to the product of the two magnetic elds threadino the disc into the sine of the time angular phase displacement existing between them, and if the angle and the lfluir fromthe potential coil 22 remain condit).A

stant, then the driving force will increase directly with the current in the Coils 25, 26. Such is usually the case within the working range of ordinary watthour meters.

The damping magnets 19, 20 are so arranged with respect to the disc 17 that the latterintercepts that part of the magnetic flux which passes between the pole tips of' representing a typical load registration curveI of a modern induction watthour meter.

' explanation of the result shown by said curve l(il) is found in the fact that the damping magnets 19, 20 -arenot the only source of magnetism through the disc that serves to create a retarding force with the rotation of the disc. The magnetic circuits which create the driving force requirethe presence of a strong A. C. magnetic field threading the discV at the air gap 10, which at the same time creates retarding forces that at a given speed of the disc will vary in a ratio which is almost as the square of the magnetic iux. It is customary,

therefore, in designing A. C. watthour meters to make the-permanent damping magnets very strong so that the flux passing through the disc and resulting from the A. C. magnetic circuits will be but a small proportion ofthe total. This, however, can only serve to minimize the effect without actually eliminating it within the commercial range of the instrument. y f

y According to our invention,we propose to provide one ormore magnetic circuits of the meter with specified reluctance paths which are controllable within the working range of the instrument, and thereby provide a driving force within` the disc which, assuming constant voltage and phase displacement as before, increases at a greater rate than the load current, and is sufficient to compensate for the increased 'damping provided, thereby resulting in a speed of rotation of the disc which is truly in proportion to the load within the entire working range of the instrument. In practice this is accomplished by applying to one or more of the-magnetic circuits of the meter magnetic shunts and air gaps associated therewith in such manner as.

mentary drawing of the magnetic circuit as sociated with the current circuit of an induction watthour meter such as that shown in Fig. 1. In'this caseV the reluctance consists of two iron parts made up of the laminations forming the return plate 21 and the series magnet 8, and the air vgap 10 within which the meter disc rotates. Since the major portion of the reluctance of the magnetic circuit is vcomposed of air, this reluctance is forall practical purposesa constant quantity, and the iux in the air gap therefor increases almost in the same ratio as the'a'mpere-turns or the magnetomotive force interlinked with this magnetic circuit. The desired correction of the load registration curve is accomplished 1n the arrangementshown in Fig. 3 by placing across thevpole tip extensions 14, 15 of `the series magnet a block 28 of magnetic material, such as iron, separated from th'e pole4 tips 14., 15 by. L-shaped strips 29, 30 of brass or other non-magnetic material. These strips or'spacers serve to mechanically support the bridge block or shunt in recesses in the sides of the pole tips 14-15, and because of their non-magnetic characteristic they also function as air gaps between the en'ds of the shunt and the pole tips 14445; The block 28 is preferably made up of laminations similar to those of the pouentialand series magnets. At

low magnetic densities the block 28 has a tendency to shunt a very considerable portion of the magnetism coming from the poles 11, 12, and thereby prevent it from crossing the .gap l0 and increasing the torque of the meter at this point of the load characteristic, but as the magnetomotive force is increased, due to increasing load, the block or shunt 28 gradually becomes saturated and within certain limits the active flux in the air gap 10 increases at a greater rate than the magnetomotive force caused by the line current. This, according to the theory already pointed out, causes the torque to increase more rapidly than the load, and the curve of registration, instead of falling off with increased load, shows a decided tendency to rise within the usual range of operation. There is produced, therefore, an effect which is similar to the compounding of D. C. machinery, resulting in a load registration curve as shown by the dotted line B in Fig. 6. The shape of the load characteristic is controllable between the desired limits and made possible through the selection for the shunt of alloys having different magnetic properties, and through the size, shape and location of the shunt or shunts within the magnetic circuits of the meter, as by suitably proportioning the materials constituting the shunt or shunts and the air gaps associated therewith the curves may be made to assume various shapes, depending upon the points at which the materials of the shunt saturate, as well as the equivalent air gaps with which they are associated.

Instead of the arrangement shown in Fig. 3, in which the series magnet is composed of a single C-shaped set of laminations, a more suitable and effective arrangement, such as that shown in Fig. 4, may be employed. In the latter arrangement instead of making the series magnet of one set of C-shaped laminations, it is composed of two halves 8i and 8h, separated not only by the air gap 16 opposite the pole extensions 14, 15, but also by an air gap 31 preferably at a point diametrically opposite the air gap 16. The two halves 8a, 8b are held in Xed relation to each other by means of two C-shaped plates 32, 33 of brass or other suitable non-magnetic material, the several parts being securely connected together in any suitable way, as by rivets 34. In this case the shunt 28 is employed as before. This arrangement provides a constant air gap 31, and further serves to separate the lower pole 9 of the potential magnet 7 from direct contact with the series magnet 8, a'construction which is desirable in this particular embodiment of our invention. In connection with the air gap 31, we provide a magnetic shunt 35 in the form of a suitable magnetic conducting plate which bridges the gap 31 and is separated from the members 81. 8b by a non-magnetic strip 36.

In the arrangement shown in Fig. 4, the

magnetic circuit interlinked with the current circuit of the series coils 25, 26 of the meter consists of the two halves 8a, 8b of the series magnet in series with the air gap 31, which in turn are in series with two magnet-ic circuits as follows: first the shunt 28 having the spacers 29, 30; second, the air gap 10 and the return plate 21. Disregarding for the present the non-inagnetic strip 36 and the shunt 35, the a-ir gap 31 adds a Very considerable reluctance to the magnetic circuit just described. The shunt 28 is so proportioned that for loads on the meter up to approximately normal load, the flux in the air gap 10 resulting from the series coils 25, 26 is almost proportional to the ampere turns or the magnetomotive force, a considerable proportion of the magnetomotive force being absorbed by the air gap 31. For increasing loa-ds the shunt 28 becomes saturated at a rate depending upon its magnetic properties, and by design is made to be just suhcient to cause the air gap flux to increase at the proper rate required for constant registration up to at least two and one-half times normal load current.

The object of providing the magnetic shunt 35 is to compensate for slight irregularities in the load curve even at the lighter loads. By reference to Fig. 6 it will be seen that there is a rather ,sudden droop at the point a in the curve A, and it is to remedy this that the shunt 35 is provided. Said shunt bridges the air gap 3-1, and it is so designed as to saturate at the proper points to change slightly the registration of the meter at light loads in order to compensate for the droop in the curve at the point a. In Figure 6 the curve C represents a typical load registration curve of a. watthour meter having the construction shown in Figure 4. y

It will also be noted that the shunt 28 in Figures 3 and 4 has a shielding action with reference to the leakage flux passing upwardly from the inner sides of the magnet structure 8, which shielding action is variable, depending upon the iiuX density in the shunt 28, and is thereby made to assist in con-` trolling the shape of the registration curve. That is to say, while the meter is operating at low loads and the shunt is below its saturation point, the leakage flux above referred to is being intercepted yby the shielding action of the shunu and is therefore prevented from penetrating the rotating disc. However, when the shunt approaches or reaches its saturation point with the imposing of an increasing load on the meter, the shielding action of the shunt diminishes, and thereafter a considerable portion of this leakage fiuX penetrates the disc and aids in causing the driving torque effective thereon to increase at a greater rate than the magnetomotive force. Thus the shielding action of the shunt also assists in securing the desired shape o" load registration curve.

Figure 5 illustrates an arrangement similar to that shown in Fig. et,4 but differing therefrom in the specilic location of the shunt 28. In the arrangement of Fig. 5 said shunt is fitted at its ends in suitablerecesses pro` vided in the extensions 14, 15 of the poles of the series magnet, and the non-magnetic strips used in connection therewith are U- shaped, as shown at 292303, instead of having the L-shape shown in Figs. 3 and 4.

As we believe is made clear by the foregoing description, our improved method of controlling the registration curve of a meter consists in applying to one or more of its mags netic circuits one or more magnet-ic shunts associated with air gaps in such manner that a considerable portion of the magnetism is shunted and prevented from crossing the air gap to increase the torque of the meter, until by increase of the magnetomotive force the shunt reaches the point of saturation, so that within certain limits the active iiux increases at a greater rate than the magnetomotive force caused bythe line current, and con sequently causes the torque to increase more rapidlytlian the load. and the curve of registration, instead of falling ott' with increased load, tends to rise. By the use of materials having the requisite magnetic properties, and through the size, shape and location of such parts within the magnetic circuits of the meter, it is therefore practicable to control the curve within rather wide limits.

TVhilc we have shown and described our invention as applied to the control of the load registration curve of an induction watthour meter, it should be understood that it is not limited to such use, but may be applied in various other types of meters and other instruments, and to the control of the voltage registration curve rather than the load registration curve, without exceeding the scope of the broader claims appended hereto.

What we claimv as our invention and desire to secure by Letters Patent., is 1. An electricV meter comprising series an potential 'electro-magnets, providing an air gap between them, an armature arranged to rotate .in said air gap, said series magnet comprising two C-shaped members separated by air gaps and firmly secured together, and magnetic shunts bridging the latter air gaps.

2. An electric meter comprising series and potential electro-magnets, providing an air gap between said magnets, an armature arranged to rotate in said air gap, a damping l magnet associated with said armature, said series magnet comprising two C-shaped members separated by air gaps and firmly secured l' together, and magnetic shunts bridging the latter air gaps.

3. An induction watthour meter comprising series and potential electro-magnets, providing an air gap threaded by flux produced by said electromagnets, an armature rotating in said air gap, said series magnet compris 'ing separated pole portions, and a shunt ex- 'leakage ilux from said series magnet, said shunt being magnetically spaced from said pole portions and being so proportioned in sectional thickness as to become saturated at heavy loads for compelling an increasing proportion of the series iux to thread said air gap and for permitting the aforesaid leakage iux to penetrate said armature.

4. An induction watthour meter comprising a series electro-magnet having two separated pole pieces deiining one side of an air gap, a potential electro-magnet having one end associated with the lower portion of said series electro-magnet and having its other end defining the other side of said air gap, an armature disc rotating in said air gap, and a. shunt extending in bridging relation between the pole pieces of said series electro-magnet in close proximity to said air gap, said series electro-magnet having extensions projecting inwardly on the side of said shrmt opposite to said air gap, said shunt serving at normal loads to bypass a portion of the series flux between said pole pieces and to shield said air gap from a portion of the leakage flux emanating from said inwardly projecting extensions, said shunt being so constructed as to become saturated at heavy loads for compelling an increasing proportion of a Series lux to thread said air gap and for permitting the aforesaid leakage flux to penetrate said armature. v

5. An electric meter comprising series and potential electro-magnets, providing anA air gap threaded by ux produced by said magnets, an armature arranged to rotate in said air gap, and means for controlling the registration curve of said meter comprising a saturatable magnetic shunt supported between the pole pieces of said series magnet, but

magnetically separated from said pole pieces. 6. An electric meter comprising series and vpotential electro-magnets, providing an air .gap between them, an armature arranged to of non-magnetic material interposed between each end of said shunt and said pole pieces.

8. An electric meter comprising series and potential electro-magnets, providing anvair gap associated therewith and threaded by the flux produced by said electro-magnets, an armature arranged to rotate in said air gap, and means for controlling the registration curve of said meter comprising a single, continuous magnetic shunt extending in bridging relation between the pole project-ions of said se,- ries magnet and disposed in close proximity to said armature, said shunt being designed to become saturated at a predetermine meter load, and non-magnetic spacing members between the ends of said shunt and said pole projections. l

9. An induction watthour meter comprising series and potential electro-magnets, providing am air gap associated therewith threaded by the iux produced by said magnets, an armature disc arranged to rotate in said air gap, the pole projections ofsaid series magnet having recesses therein, angularly shaped non-magnetic strips in said recesses, and a laminated shunt having its ends engaging in said recesses with said strips interposed between the ends of said shunt and said pole projections, said shunt having one of its surfaces approximately flush with the pole projection faces of said series magnet so as to serve as a shield for preventing the leakage flux from the inner sides of the pole projection of said lseries magnet from entering said air gap, said shunt being designed to become saturated at a predetermined load and thereafter permitting t-he aforesaid leakage ux to pass into said air gap and act on said armature disc.

l0. An electric watthour meter, characterized by a saturatable magnetic shunt placed between the pole pieces of the series magnet of said meter in spaced relation to both said pole pieces and in such relation to the armature as to shield said armature from leakage flux from said circuit until said shunt be- ,comes saturated, whereupon leakage flux will penetrate the armature.

FRED KURZ. ROSCOE VVILMETH. 

